Uv light emitting device

ABSTRACT

Disclosed herein is a UV light emitting device. The UV light emitting device includes a first conductive type semi-conductor layer, an anti-cracking layer disposed on the first conductive type semiconductor layer, an active layer disposed on the anti-cracking layer, and a second conductive type semiconductor layer disposed on the active layer, wherein the anti-cracking layer includes first lattice points and second lattice points disposed at an interface between the first conductive type semiconductor layer and the anti-cracking layer, the first lattice points are connected to lattices of the first conductive type semiconductor layer, and the second lattice points are not connected to the lattices of the first conductive type semiconductor layer.

TECHNICAL FIELD

Exemplary embodiments of the present disclosure relate to an ultraviolet(UV) light emitting device, and more particularly, to a UV lightemitting device including an anti-cracking layer capable of preventinggeneration of cracks to improve crystallinity of semiconductor layers.

BACKGROUND ART

Since a UV light emitting device emits light having a relatively shortpeak wavelength (generally, a peak wavelength of 400 nm or less), alight emitting region is formed of AlGaN containing 10% or more of Al infabrication of a UV light emitting device using a nitride semiconductor.In such a UV light emitting device, if n-type and p-type nitridesemiconductor layers have smaller energy band-gaps than energy of UVlight emitted from an active layer, UV light emitted from the activelayer can be absorbed into the n-type and p-type nitride semiconductorlayers in the light emitting device. Then, the light emitting devicesuffers from significant deterioration in luminous efficacy.Accordingly, not only the active layer of the UV light emitting device,but also other semiconductor layers placed in a light emitting directionof the UV light emitting device, particularly, an n-type semiconductorlayer, contain 10% or more of Al.

In fabrication of a UV light emitting device, a sapphire substrate isgenerally used as a growth substrate. However, when Al_(x)Ga_((1-x))Nlayer (0.1≦×≦1) containing 10% or more of Al is grown on the sapphiresubstrate, the UV light emitting device suffers from cracking orbreaking caused by thermal or structural deformation due to a high Alcontent. This problem is caused by lattice mismatch or difference incoefficient of thermal expansion between the sapphire substrate and theAl_(x)Ga_((1-x))N layer (0.1≦×≦1). Specifically, due to difference incoefficient of thermal expansion between the sapphire substrate having arelatively high coefficient of thermal expansion and a nitridesemiconductor having a relatively low coefficient of thermal expansion,a wafer suffers from bowing into a concave shape upon growth of thenitride semiconductor at high temperature (at about 1000° C. or more).When the growth temperature is decreased again, the wafer is flattenedagain or bowed into a convex shape. Due to bowing of the wafer, cracksare generated in the nitride semiconductor, thereby causingdeterioration in production yield and quality of light emitting devices.

DISCLOSURE OF INVENTION Technical Problem

Exemplary embodiments of the present disclosure provide a UV lightemitting device that includes semiconductor layers having goodcrystallinity and has an anti-cracking structure.

Exemplary embodiments of the present disclosure provide a vertical-typeUV light emitting device that includes semiconductor layers having goodcrystallinity

Solution to Problem

In accordance with aspects of the present disclosure, a UV lightemitting device includes: a first conductive type semiconductor layer;an anti-cracking layer disposed on the first conductive typesemiconductor layer; an active layer disposed on the anti-crackinglayer; and a second conductive type semiconductor layer disposed on theactive layer, wherein the anti-cracking layer includes first latticepoints and second lattice points disposed at an interface between thefirst conductive type semiconductor layer and the anti-cracking layer,the first lattice points are connected to lattices of the firstconductive type semiconductor layer, and the second lattice points arenot connected to the lattices of the first conductive type semiconductorlayer.

In accordance with various aspects of the present disclosure, a UV lightemitting device includes: a first conductive type semiconductor layer;an anti-cracking layer disposed on the first conductive typesemiconductor layer; an active layer disposed on the anti-crackinglayer; and a second conductive type semiconductor layer disposed on theactive layer, wherein a portion above an interface between the firstconductive type semiconductor layer and the anti-cracking layer has ahigher lattice density than a portion under the interface.

In accordance with various aspects of the present disclosure, a methodof fabricating a UV light emitting device includes: forming a firstconductive type semiconductor layer on a growth substrate; forming ananti-cracking layer on the first conductive type semiconductor layer;forming an active layer on the anti-cracking layer; and forming a secondconductive type semiconductor layer on the active layer, wherein theanti-cracking layer is formed at a lower growth temperature than thefirst conductive type semiconductor layer, and the forming theanti-cracking layer includes forming first lattice points not connectedto lattices of the first conductive type semiconductor layer.

Advantageous Effects of Invention

According to exemplary embodiments, a UV light emitting device includesan anti-cracking layer disposed on a first conductive type semiconductorlayer to improve crystallinity of semiconductor layers, therebyimproving reliability and efficiency of the UV light emitting device. Inaddition, according to exemplary embodiments, a method of fabricating aUV light emitting device includes forming an anti-cracking layer on afirst conductive type semiconductor layer, thereby facilitatingseparation of a growth substrate from the first conductive typesemiconductor layer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 to FIG. 7 are sectional views of a UV light emitting deviceaccording to exemplary embodiments and a method of fabricating the same.

FIG. 8 is a graph illustrating a method of forming an anti-crackinglayer according to exemplary embodiments.

FIG. 9a to FIG. 10b are sectional views illustrating a method of formingan anti-cracking layer according to exemplary embodiments.

FIG. 11a and FIG. 11b are enlarged sectional views of a relationshipbetween a first conductive type semiconductor layer and an anti-crackinglayer according to exemplary embodiments.

FIG. 12 is a sectional view of a UV light emitting device according toother exemplary embodiments and a method of fabricating the same.

FIG. 13 to FIG. 16 are sectional views of a UV light emitting deviceaccording to further exemplary embodiments and a method of fabricatingthe same.

MODE FOR THE INVENTION

A UV light emitting device according to various exemplary embodimentsand a method of fabricating the same can be realized in various ways.

A UV light emitting device according to some exemplary embodimentsincludes a first conductive type semiconductor layer; an anti-crackinglayer disposed on the first conductive type semiconductor layer; anactive layer disposed on the anti-cracking layer; and a secondconductive type semiconductor layer disposed on the active layer,wherein the anti-cracking layer includes first lattice points and secondlattice points disposed at an interface between the first conductivetype semiconductor layer and the anti-cracking layer, the first latticepoints are connected to lattices of the first conductive typesemiconductor layer, and the second lattice points are not connected tothe lattices of the first conductive type semiconductor layer.

At the interface between the first conductive type semiconductor layerand the anti-cracking layer, the anti-cracking layer can have a higherdensity of lattice points per unit area than the first conductive typesemiconductor layer.

The first conductive type semiconductor layer can include a crackinduction portion in which a lattice distance gradually increases in anupward direction.

A horizontal lattice distance in an uppermost portion of the crackinduction portion can be greater than an average horizontal latticedistance in the first conductive type semiconductor layer.

At least some of the second lattice points can be placed on the crackinduction portion.

The anti-cracking layer can include a plurality of layers, and at leastone of the plurality of layers can include a lattice point not connectedto a lattice in a layer under the at least one layer.

The plurality of layers of the anti-cracking layer can constitute asuper lattice structure.

Each of the first conductive type semiconductor layer and theanti-cracking layer can include a nitride-based semiconductor includingAl and Ga.

The anti-cracking layer can further include indium (In), the activelayer can have a multi-quantum well structure including barrier layersand well layers, and the barrier layer can include a nitride-basedsemiconductor containing Al, Ga and In.

The light emitting device can further include a growth substratedisposed under the first conductive type semiconductor layer, whereinthe growth substrate can have a higher coefficient of thermal expansionthan the first conductive type semiconductor layer.

The UV light emitting device can further include a super lattice layerdisposed between the anti-cracking layer and the active layer.

In some exemplary embodiments, the UV light emitting device can furtherinclude a first electrode disposed under the first conductive typesemiconductor layer and electrically connected to the first conductivetype semiconductor layer; and a second electrode disposed on an upperside of the second conductive type semiconductor layer and electricallyconnected to the second conductive type semiconductor layer.

The anti-cracking layer can have a thickness of 5 nm to 15 nm.

A UV light emitting device according to other exemplary embodimentsincludes: a first conductive type semiconductor layer; an anti-crackinglayer disposed on the first conductive type semiconductor layer; anactive layer disposed on the anti-cracking layer; and a secondconductive type semiconductor layer disposed on the active layer,wherein a portion above an interface between the first conductive typesemiconductor layer and the anti-cracking layer has a higher latticedensity than a portion under the interface.

The anti-cracking layer can be grown at a lower growth temperature thanthe first conductive type semiconductor layer, and during growth of theanti-cracking layer, a lattice not connected to a lattice of the firstconductive type semiconductor layer can be formed.

A method of fabricating a UV light emitting device according to otherexemplary embodiment can include: forming a first conductive typesemiconductor layer on a growth substrate; forming an anti-crackinglayer on the first conductive type semi-conductor layer; forming anactive layer on the anti-cracking layer; and forming a second conductivetype semiconductor layer on the active layer, wherein the anti-crackinglayer is formed at a lower growth temperature than the first conductivetype semiconductor layer, and the forming the anti-cracking layerincludes forming first lattice points not connected to lattices of thefirst conductive type semiconductor layer.

During the formation of the anti-cracking layer, an inner temperature ofa growth chamber can be gradually decreased for at least some period oftime.

The first conductive type semiconductor layer can be grown at a firsttemperature, the active layer can be grown at a second temperature lowerthan the first temperature, and the anti-cracking layer can be grownduring lowering the temperature from the first temperature to the secondtemperature.

During lowering the temperature from the first temperature to the secondtemperature, a crack induction portion can be formed in the firstconductive type semi-conductor layer, and first lattice points notconnected to lattices of the first conductive type semiconductor layerof the anti-cracking layer can be formed in the crack induction portion.

The forming the anti-cracking layer can further include forming secondlattice points connected to lattices of the first conductive typesemiconductor layer.

The forming the anti-cracking layer can include growing theanti-cracking layer using remaining sources among sources introducedinto a growth chamber to form the first conductive type semiconductorlayer instead of introducing a separate source into the growth chamberduring formation of the anti-cracking layer.

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Thefollowing embodiments are provided by way of example so as to fullyconvey the spirit of the present disclosure to those skilled in the artto which the present disclosure pertains. Accordingly, the presentdisclosure is not limited to the embodiments disclosed herein and canalso be implemented in different forms. In the drawings, widths,lengths, thicknesses, and the like of elements can be exaggerated forclarity and descriptive purposes. It will be understood that when anelement such as a layer, film, region or substrate is referred to asbeing “on” another element, it can be directly on the other element orintervening elements can also be present. In contrast, when an elementis referred to as being “directly on” another element, there are nointervening elements present. Throughout the specification, likereference numerals denote like elements having the same or similarfunctions.

It should be understood that respective composition ratios, growthmethods, growth conditions, and thicknesses of semiconductor layersdescribed below are provided for illustration only and do not limit thescope of the present disclosure. For example, when a certainsemiconductor layer is represented by AlGaN, a composition ratio of Aland Ga in the semiconductor layer can be determined in various ways asneeded. Furthermore, semiconductor layers described below can be grownby various methods generally known to person having ordinary knowledgein the art (hereinafter, “those skilled in the art”), for example, metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE),hydride vapor phase epitaxy (HVPE), and the like. In the followingexemplary embodiments, semiconductor layers will be described as beinggrown in the same chamber by MOCVD. During growth of semiconductorlayers, sources introduced into a chamber can be selected from sourcesknown to those skilled in the art, for example, TMGa and TEGa as Gasources, TMAl and TEAl as Al sources, TMIn and TEIn as In sources, andNH₃ as an N source, without being limited thereto, other implementationsare also possible.

Although a method of fabricating a single UV light emitting device isdescribed in the following exemplary embodiments, it should beunderstood that the present disclosure is not limited thereto. Thefollowing exemplary embodiments can also be applied to fabrication of awafer for fabrication of a plurality of light emitting devices on asubstrate having a size of several inches or more.

FIG. 1 to FIG. 7 are sectional views of a UV light emitting deviceaccording to exemplary embodiments and a method of fabricating the same.FIG. 1 to FIG. 7 sequentially illustrate the method of fabricating alight emitting device according to the exemplary embodiment. However, itshould be understood that the method of fabricating the light emittingdevice according to this exemplary embodiment is not limited to thesequence described below. In addition, FIG. 8 is a graph illustrating amethod of forming an anti-cracking layer according to one exemplaryembodiment, FIG. 9a to FIG. 10b are sectional views of methods offorming anti-cracking layers according to exemplary embodiments, andFIG. 11a and FIG. 11b are enlarged sectional views of a relationshipbetween a first conductive type semiconductor layer and each ofanti-cracking layers according to exemplary embodiments.

Referring to FIG. 1, a growth substrate 110 is prepared. Furthermore,the fabrication method according to this exemplary embodiment canfurther include forming a buffer layer 121 on the growth substrate 110.

The growth substrate 110 can be selected from any substrates that allowgrowth of nitride semiconductor layers thereon, and can be, for example,a sapphire substrate, a silicon carbide substrate, a spinel substrate,or a nitride substrate such as a GaN substrate or an AN substrate.Particularly, in this exemplary embodiment, the growth substrate 110 canbe a sapphire substrate. Further, the growth substrate 110 according tothis exemplary embodiment can have a lower coefficient of thermalexpansion than nitride semiconductor layers formed by the followingprocesses described below.

The buffer layer 121 can include Ga, for example, GaN. The buffer layer121 can be grown to a thickness of about 25 nm or less on the growthsubstrate 110, and can be grown at a temperature of about 600° C. and apressure of 600 Torr. Particularly, in an exemplary embodiment whereinthe growth substrate 110 is a sapphire substrate, the buffer layer 121can act as a nucleus layer so as to allow growth of other semi-conductorlayers thereon, and can also serve to relieve stress due to a differencein lattice parameter between the sapphire substrate and othersemiconductor layers formed thereon by the following processes. Forexample, the buffer layer 121 can include a 2D growth layer and a 3Dgrowth layer. In this exemplary embodiment, the buffer layer 121 isformed of a nitride semiconductor including GaN, thereby furtherfacilitating separation of the growth substrate through laser lift-off.In some exemplary embodiments, the buffer layer 121 can also be omitted,as needed.

Then, referring to FIG. 2, a base nitride layer 123 is formed on thegrowth substrate 110.

The base nitride layer 123 can include Ga, and can include, for example,an undoped GaN layer. The base nitride layer 123 can be grown in agrowth chamber into which a Ga source and an N source are introduced, ata temperature of about 900° C. to 1100° C. and a pressure of about 200Torr. The base nitride layer 123 can be grown to a thickness of about 1μm to 1.2 μm. Alternatively, the base nitride layer 123 can include anAl-containing nitride semiconductor. In this exemplary embodiment, theAl content can be adjusted to allow the base nitride layer 123 to absorba laser beam in a laser lift-off process. For example, the base nitridelayer 123 can contain about 40% or less of Al, preferably 20% or less ofAl.

In the method of fabricating a light emitting device according to thisexemplary embodiment, the base nitride layer 123 is grown on the growthsubstrate 110, and can absorb a laser beam emitted during a process ofseparating the growth substrate 110. Accordingly, the method offabricating a light emitting device according to this exemplaryembodiment allows easy separation of the growth substrate 110. Inaddition, GaN grown on the growth substrate 110 has a lower crystaldefect density than AlN. Accordingly, the base nitride layer 123including GaN having relatively good crystallinity is formed beforegrowth of an n-type semiconductor layer, thereby improving overallcrystallinity of the light emitting device, as compared with growth ofan AlN layer before growth of the n-type semiconductor layer in therelated art.

In some exemplary embodiments, the buffer layer 121 and/or the basenitride layer 123 can be omitted, as needed. For example, in fabricationof a horizontal type light emitting device, the base nitride layer 123can be omitted.

Then, referring to FIG. 3, a first conductive type semiconductor layer130 is formed on the growth substrate 110, that is, on the base nitridelayer 123.

The first conductive type semiconductor layer 130 can be grown bysupplying group III element sources including an Al source, an N source,and a dopant source into the growth chamber. For example, the firstconductive type semiconductor layer 130 can be grown by supplying TMAland TMGa as the group III element sources, NH₃ as the N source, andsilane as the dopant source into the growth chamber. In the growthchamber, the growth temperature can be set in the range of about 1050°C. to 1150° C. and although the growth pressure is not particularlylimited, the growth pressure can be, for example, about 200 Torr. Thefirst conductive type semiconductor layer 130 grown can include Si in aconcentration of, for example, 1×10¹⁸ cm⁻¹ or more, and thus exhibitn-type conductivity. Here, it should be understood that the dopant forthe first conductive type semiconductor layer 130 is not limited to Siand can include various dopants such as Ge, C, Sn, and the like.

The first conductive type semiconductor layer 130 can be composed of asingle layer or multiple layers. In an exemplary embodiment wherein thefirst conductive type semiconductor layer 130 is composed of multiplelayers, the first conductive type semiconductor layer 130 can include acontact layer, a clad layer, and the like, and can further include asuper lattice layer.

Referring to FIG. 4, an anti-cracking layer 140 is formed on the firstconductive type semiconductor layer 130. Next, with reference to FIG. 8to FIG. 11b , exemplary embodiments of the anti-cracking layer 140 willbe described in detail. FIG. 8 is a graph illustrating a method offorming an anti-cracking layer 140 according to one exemplaryembodiment; and FIG. 9a to FIG. 10b are sectional views illustrating amethod of forming an anti-cracking layer 140 according to exemplaryembodiments. In addition, FIG. 11a and FIG. 11b are enlarged sectionalviews of a relationship between the first conductive type semiconductorlayer 130 and the anti-cracking layer 140 according to the exemplaryembodiments, in which lattices of the first conductive typesemiconductor layer 130 and the anti-cracking layer 140 areschematically shown.

First, referring to FIG. 8, FIG. 9a and FIG. 9b , with the innertemperature of the growth chamber set to a first temperature Ti, thefirst conductive type semiconductor layer 130 is grown for a firstperiod of time P1. As described above, the first temperature T1 can be atemperature ranging from about 1050° C. to 1150° C., for example, about1100° C. Further, the first conductive type semiconductor layer 130 canbe grown by supplying group III element sources (for example, TMAl andTMGa), an N source (for example, NH₃) and a dopant source (for example,silane) into the growth chamber.

During growth of the first conductive type semiconductor layer 130, thewafer with the first conductive type semiconductor layer 130 grown onthe growth substrate 110 is deformed into a concave shape, as shown inFIG. 9a . This deformation results from a difference in coefficient ofthermal expansion between nitride semiconductor layers including thefirst conductive type semiconductor layer 130 and the growth substrate110 which has a higher coefficient of thermal expansion than nitridesemiconductor layers, as described above. Specifically, the growthtemperature of the buffer layer 121 initially grown on the growthsubstrate 110 (for example, about 600° C.) is lower than the growthtemperature of the first conductive type semiconductor layer 130.Accordingly, after growth of the buffer layer 121, when the innertemperature of the growth chamber is increased to a high temperature ofabout 1000° C. or more for growth of the first conductive typesemiconductor layer 130, an expansion rate of the substrate becomeshigher than the expansion rate of the nitride semiconductors, therebycausing deformation of the wafer into a concave shape, that is, a bowingphenomenon.

Here, some of lattices 131 in the first conductive type semiconductorlayer 130 can be arranged as shown in FIG. 9b . In FIG. 9b , thelattices 131 are shown as being generally arranged in a directionparallel to a growth direction (that is, in a perpendicular directionwith respect to a growth plane of the growth substrate 110) forconvenience of description. Thus, the lattices of the first conductivetype semiconductor layer 130 according to this exemplary embodiment arenot limited thereto.

Next, referring to FIG. 8, FIG. 10a and FIG. 10b , the anti-crackinglayer 140 is formed on the first conductive type semiconductor layer130. The anti-cracking layer 140 can be formed at a lower temperaturethan the first conductive type semiconductor layer 130. In addition, theanti-cracking layer 140 can be grown in the course of decreasing theinner temperature of the growth chamber to grow a super lattice layer150 or an active layer 160 on the first conductive type semiconductorlayer 130. As shown in FIG. 8, after growth of the first conductive typesemiconductor layer 130, the anti-cracking layer 140 can be grown for asecond period of time P2 in the course of decreasing the innertemperature of the growth chamber from the first temperature Ti to asecond temperature T2 at which the super lattice layer 150 or the activelayer 160 are grown on the first conductive type semiconductor layer130. In this process, supply of the sources for growth of the firstconductive type semiconductor layer 130 is maintained, whereby theanti-cracking layer 140 can be grown on the first conductive typesemiconductor layer 130. Thus, the anti-cracking layer 140 can be grownusing the same sources as those for the first conductive typesemiconductor layer 130. However, the present disclosure is not limitedthereto, and for the second period of time P2, for which theanti-cracking layer 140 is grown, TEGa can be further supplied as thegroup III element source into the growth chamber, or can be supplied asthe group III element source into the growth chamber instead of TMGa.Here, depending upon whether supply of dopant sources is stopped or not,the anti-cracking layer 140 can be doped to an n-type layer or in anundoped state. Furthermore, the anti-cracking layer 140 can be grownwithout supplying the sources into the growth chamber, in the course ofdecreasing the inner temperature of the growth chamber from the firsttemperature T1 to the second temperature T2. Even in the case where aseparate source is not supplied into the growth chamber during thetemperature decrease procedure, the anti-cracking layer 140 can be grownby the remaining sources supplied for growth of the first conductivetype semiconductor layer 130.

In some exemplary embodiments, during growth of the anti-cracking layer140, an indium (In) source can be further supplied into the growthchamber and the anti-cracking layer 140 can include AlInGaN. When thebarrier layer in the active layer 160 contains indium (In), theanti-cracking layer 140 is formed to include AlInGaN and thus furtherimproves crystal quality of the active layer 160 by relieving latticemismatch.

The second temperature T2 can range from about 800° C. to 900° C. andmay, for example, be about 840° C. In addition, the second period oftime P2 can range from about 8 minutes to 15 minutes, specifically,about 10 minutes to 12 minutes. Accordingly, the anti-cracking layer 140can be formed to a thickness of about 5 nm to 15 nm. If the secondperiod of time P2 is too long, the anti-cracking layer 140 can becometoo thick, thereby deteriorating the anti-cracking function of theanti-cracking layer 140. Preferably, the second period of time P2 isadjusted such that the anti-cracking layer 140 has the above thickness.It should be understood that the present disclosure is not limitedthereto.

As the inner temperature of the growth chamber is decreased from thefirst temperature T1 to the second temperature T2, the bowing phenomenonof the wafer including the growth substrate 110 and the nitridesemiconductor layers 121, 123, 130, 140 is relieved. That is, as theinner temperature of the growth chamber is lowered for the second periodof time P2, the radius of curvature of the wafer can be decreased. Asshown in FIG. 10a , as compared with the degree of bowing of the wafer(as indicated by a dotted line) at the first temperature T1, the degreeof bowing of the wafer can be reduced as the inner temperature of thegrowth chamber is decreased to the second temperature T2.

At this time, the probability that cracks are generated at an upperportion of the first conductive type semiconductor layer 130 canincrease with decreasing degree of bowing of the wafer, that is, withdecreasing radius of curvature of the wafer deformed into a concaveshape. Specifically, as shown in FIG. 10b , some of the lattices 131 ofthe first conductive type semiconductor layer 130 can have a graduallyincreasing lattice distance in a growth direction of the firstconductive type semiconductor layer 130. In a portion where the distancebetween the lattices 131 gradually increases in the growth direction ofthe first conductive type semiconductor layer 130, the lattices can bedisconnected from each other and this portion has a high probability ofcracking. Thus, after decrease of the inner temperature of the growthchamber to the second temperature T2, the first conductive typesemiconductor layer 130 can include a crack induction portion 132. Anuppermost portion of the crack induction portion 132 can have a greaterhorizontal lattice distance than an average horizontal lattice distancein the first conductive type semiconductor layer 130. In this exemplaryembodiment, some lattices 141 in the anti-cracking layer 140 can beplaced on the crack induction portion 132.

Next, referring to FIG. 11a , the anti-cracking layer 140 will bedescribed in more detail.

As shown in FIG. 11a , the anti-cracking layer 140 includes latticepoints 142, 136 placed at an interface between the anti-cracking layer140 and the first conductive type semiconductor layer 130. Although amajority of the lattices 141 of the anti-cracking layer 140 can beconnected to the lattices 131 of the first conductive typesemi-conductor layer 130, some lattices 141 of the anti-cracking layer140 are not connected to the lattices 131 of the first conductive typesemiconductor layer 130. Thus, forming the anti-cracking layer 140 caninclude forming lattice points not connected to the lattices 131 of thefirst conductive type semiconductor layer 130. That is, theanti-cracking layer 140 includes first lattice points 136 that areplaced at the interface 135 and are connected to the lattices 135 of thefirst conductive type semiconductor layer 130, and second lattice points142 that are placed at the interface 135 and are not connected to thelattices 131 of the first conductive type semiconductor layer 130.Accordingly, at the interface 135 between the first conductive typesemiconductor layer 130 and the anti-cracking layer 140, theanti-cracking layer 140 can have a higher density of lattice points perunit area than the first conductive type semiconductor layer 130.Further, a portion above the interface 135 between the first conductivetype semi-conductor layer 130 and the anti-cracking layer 140 can have ahigher lattice density than a portion under the interface 135.

In particular, at least some of the second lattice points 142 of theanti-cracking layer 140 can be placed on the crack induction portion 132of the first conductive type semi-conductor layer 130. As describedabove, as the inner temperature of the growth chamber is decreased tothe second temperature T2, the distance between some lattices 141 iswidened on the first conductive type semiconductor layer 130, so thatthe crack induction portion 132, in which the lattice distance graduallyincreases upwards, can be generated. In the course of decreasing theinner temperature of the growth chamber from the first temperature T1 tothe second temperature T2, the second lattice points 142 can be formedon the crack induction portion 132, and the lattices 141 can be formedin the anti-cracking layer 140 so as to be connected to the secondlattice points 142. That is, the anti-cracking layer 140 includes thesecond lattice points 142 placed at the interface 135 and not connectedto the lattices of the first conductive type semi-conductor layer 130,thereby preventing generation of cracks in the first conductive typesemiconductor layer 130.

Specifically, when defects occur due to separation of lattices in thecrack induction portion 132 of the first conductive type semiconductorlayer 130, a probability that cracks are generated in the firstconductive type semiconductor layer 130 increases due to the defects.Particularly, in a post process in fabrication of the light emittingdevice, when the process temperature is decreased below the secondtemperature T2, the wafer can be deformed from a concavely bowed shapeinto a convexly bowed shape. In this case, the probability that cracksare generated in the first conductive type semi-conductor layer 130increases rapidly. According to this exemplary embodiment, theanti-cracking layer 140 including the second lattice points 142 isformed on the first conductive type semiconductor layer 130, therebyallowing additional lattices to be placed on the crack induction portionof the first conductive type semiconductor layer 130. The lattices 141connected to such second lattice points 142 can relieve stress appliedto the crack induction portion 132 of the first conductive typesemiconductor layer 130. Further, even when separation of the latticesoccurs in the crack induction portion 132, the lattices 141 connected tothe second lattice points 142 can shield defects, which are caused byseparation of the lattices in the first conductive type semi-conductorlayer 130, from expanding and developing into cracks or frompropagating. As a result, defect and crack density of the firstconductive type semiconductor layer 130 can be decreased, therebyimproving crystallinity of the first conductive type semi-conductorlayer 130.

Furthermore, in a UV light emitting device, which can include anAl-containing nitride semiconductor layer, an Al-containing nitridesemiconductor, for example, a nitride semiconductor such as AlGaN, has alower coefficient of thermal expansion than GaN. Accordingly, infabrication of the UV light emitting device in which the firstconductive type semiconductor layer 130 is formed of the Al-containingnitride semiconductor, the wafer can suffer from a severer bowingphenomenon than in fabrication of a blue light emitting device in whichthe first conductive type semi-conductor layer 130 is formed of GaN.That is, upon deformation, the wafer in which the first conductive typesemiconductor layer 130 is formed of AlGaN has a larger curvature thanthe wafer in which the first conductive type semiconductor layer 130 isformed of GaN. Accordingly, when the process applied to fabrication of atypical blue light emitting device is applied to the UV light emittingdevice, there is a high probability that the nitride semiconductorlayers of the light emitting device will suffer from defects such ascracks. On the other hand, according to this exemplary embodiment, theanti-cracking layer 140 is formed on the first conductive typesemi-conductor layer 130 to reduce the probability that cracks aregenerated in the first conductive type semiconductor layer 130, therebyproviding a UV light emitting device in which not only the firstconductive type semiconductor layer 130 but also the active layer 160and a second conductive type semiconductor layer 170 formed in thefollowing process have good crystallinity.

Furthermore, the anti-cracking layer 140 can be naturally formed bymaintaining supply of sources to the growth chamber or by adding aspecific source to the growth chamber in the course of decreasing theinner temperature of the growth chamber in order to form the superlattice layer 150 or the active layer 160 after formation of the firstconductive type semiconductor layer 130. Thus, according to thisexemplary embodiment, it is possible to provide a UV light emittingdevice including semiconductor layers having improved crystallinitywhile maintaining the fabrication process of a typical UV light emittingdevice.

According to other exemplary embodiments, the anti-cracking layer can becomposed of a plurality of layers. Among the plurality of anti-crackinglayers 240 a to 240 d, at least one layer can include lattice points notconnected to lattices of other layers disposed under the at least onelayer. Thus, at an interface between two layers of at least some pairsof layers continuously stacked one above another among the anti-crackinglayers 240 a to 240 d, an upper-side anti-cracking layer can have ahigher density of lattice points per unit area than a lower-sideanti-cracking layer.

Specifically, referring to FIG. 11b , an anti-cracking layer 240 caninclude first to fourth anti-cracking layers 240 a, 240 b, 240 c, 240 d.The first anti-cracking layer 240 a is placed on the first conductivetype semiconductor layer 130 and can include first lattice points 136connected to the lattices 131 of the first conductive typesemi-conductor layer 130 and second lattice points 242 a not connectedto the lattices 131 of the first conductive type semiconductor layer130. Thus, at an interface 135 between the first conductive typesemiconductor layer 130 and the first anti-cracking layer 240 a, thefirst anti-cracking layer 240 a can have a higher density of latticepoints per unit area than the first conductive type semiconductor layer130. Particularly, at least some of the second lattice points 242 a ofthe first anti-cracking layer 240 a can be placed on the crack inductionportion 132 of the first conductive type semiconductor layer 130.

Similarly, the second anti-cracking layer 240 b is placed on the firstanti-cracking layer 240 a and can include first lattice points 246 aconnected to lattices 241 a of the first anti-cracking layer 240 a andsecond lattice points 242 b not connected to the lattices 241 a of thefirst anti-cracking layer 240 a. Thus, at an interface between the firstanti-cracking layer 240 a and the second anti-cracking layer 240 b, thesecond anti-cracking layer 240 b can have a higher density of latticepoints per unit area than the first anti-cracking layer 240 a. Thisrelationship can also be applied to a relationship between the secondanti-cracking layer 240 b and the third anti-cracking layer 240 c and toa relationship between the third anti-cracking layer 240 c and thefourth anti-cracking layer 240 d.

In some exemplary embodiments, at an interface between two adjacentanti-cracking layers among the plurality of anti-cracking layers, anupper-side anti-cracking layer can have the same density of latticepoints as a lower-side anti-cracking layer. For example, as shown inFIG. 11b , at an interface between the first anti-cracking layer 240 aand the second anti-cracking layer 240 b, the first anti-cracking layer240 a can have the same density of lattice points per unit area as thesecond anti-cracking layer 240 b.

According to this exemplary embodiment, the anti-cracking layer 240includes the plurality of anti-cracking layers 240 a, 240 b, 240 c, 240d, thereby allowing formation of an anti-cracking layer that includeslattice points not connected to lattices of another anti-cracking layerplaced at a lower side. As a result, generation of defects or cracks dueto separation of lattices can be more effectively prevented.

On the other hand, the plurality of anti-cracking layers 240 a, 240 b,240 c, 240 d can include nitride semiconductors having differentcomposition ratios, and can be formed in a structure wherein a pluralityof layers is repeatedly stacked in a certain cycle. Furthermore, theplurality of anti-cracking layers 240 a, 240 b, 240 c, 240 d canconstitute a super lattice structure.

Although the anti-cracking layer 240 includes four layers in the aboveexemplary embodiment, it should be understood that the presentdisclosure is not limited thereto. The anti-cracking layer 240 caninclude at least two layers.

Referring to FIG. 5 again, the super lattice layer 150 can be formed onthe anti-cracking layer 140. The super lattice layer 150 can have astructure wherein at least two layers are repeatedly stacked one aboveanother. The at least two layers can include nitride semiconductors, forexample, an AlGaN/GaN stack structure, an AlGaN/AlGaN stack structure,and the like. The super lattice layer 150 can be formed at the secondtemperature T2. The super lattice layer 150 blocks defects such asdislocations or cracks from propagating from the anti-cracking layer 140to the active layer 160, thereby preventing deterioration incrystallinity of the active layer 160. Accordingly, the UV lightemitting device according to this exemplary embodiment can have improvedinternal quantum efficiency. In some exemplary embodiments, the superlattice layer 150 can be omitted.

Then, referring to FIG. 6, the active layer 160 is formed on the superlattice layer 150.

The active layer 160 can include (Al, Ga, In)N and can emit light havinga peak wavelength in a predetermined UV range through adjustment of acomposition ratio of nitride semiconductors. The active layer 160 caninclude barrier layers (not shown) and well layers (not shown)alternately stacked one above another to form a multi-quantum well (MQW)structure. For example, the active layer 160 can be obtained by formingbarrier layers and well layers using an Al-containing nitridesemiconductor at a temperature of about 700° C. to 900° C. and apressure of about 100 Torr to 400 Torr. Furthermore, the barrier layersand/or the well layers of the active layer 160 can contain indium (In),and can be formed of, for example, a quaternary nitride semiconductorsuch as AlInGaN. In the structure wherein the active layer 160 containsIn, an In source can be introduced into the growth chamber during growthof the anti-cracking layer 140 such that the anti-cracking layer 140includes In. Accordingly, lattice mismatch between the anti-crackinglayer 140 and the active layer 160, particularly, between the barrierlayers of the active layer 160, can be relieved, thereby improvingcrystallinity of the active layer 160.

In addition, among the barrier layers of the active layer 160, thenearest barrier layer to the first conductive type semiconductor layer130 can have a higher Al content than other barrier layers. The nearestbarrier layer to the first conductive type semi-conductor layer 130 isformed to have a greater band gap than the other barrier layers, wherebyoverflow of electrons can be effectively prevented through decrease inmovement speed of the electrons.

Next, referring to FIG. 7, a second conductive type semiconductor layer170 is formed on the active layer 160. As a result, a light emittingdevice as shown in FIG. 7 can be provided.

The second conductive type semiconductor layer 170 can be formed on theactive layer 160, and can be formed to a thickness of about 0.2 μm orless by supplying an Al-containing group III element source, an N sourceand a dopant source into a chamber at a temperature of about 900° C. to1000° C. and a pressure of about 100 Torr to 400 Torr. The secondconductive type semiconductor layer 170 can include a nitridesemi-conductor such as AlGaN or GaN, and can further include a dopant,such as Mg, with which a p-type layer is formed.

Furthermore, the second conductive type semiconductor layer 170 canfurther include a delta-doping layer (not show) to reduce ohmic contactresistance, and can further include an electron-blocking layer (notshown). The electron-blocking layer can include an AlGaN layer. Further,the electron-blocking layer can include a first electron-blocking layer(not shown) and a second electron-blocking layer (not shown) placed onthe first electron-blocking layer, wherein the first electron-blockinglayer can have a higher Al content than the second electron-blockinglayer.

In some embodiments, the first conductive type semiconductor layer 130,the active layer 140 and the second conductive type semiconductor layer150 can further include additional layers. For example, thesemiconductor layers 130, 140, 150 can further include a super latticelayer, a high density doped layer, and the like, thereby improvingcrystallinity and luminous efficacy of the light emitting device.

The light emitting device of FIG. 7 can be fabricated to have variousstructures through additional processes. Hereinafter, the structure ofthe UV light emitting device will be described through exemplaryembodiments with reference to FIG. 12 to FIG. 16. However, it should beunderstood that the present disclosure is not limited to the followingexemplary embodiments.

First, FIG. 12 is a sectional view of a UV light emitting deviceaccording to exemplary embodiments and a method of fabricating the same.

Referring to FIG. 12, the UV light emitting device includes a growthsubstrate 110, a first conductive type semiconductor layer 130, ananti-cracking layer 140, an active layer 160, a second conductive typesemiconductor layer 170, a first electrode 181, and a second electrode183. The UV light emitting device can further include a buffer layer121, a base nitride layer 123, and a super lattice layer 150.

The UV light emitting device of FIG. 12 can be fabricated from the UVlight emitting device of FIG. 7. From the UV light emitting device ofFIG. 7, the second conductive type semiconductor layer 170, the activelayer 160 and the super lattice layer 150 are partially removed suchthat the first conductive type semiconductor layer 130 is partiallyexposed, and the first and second electrodes 181, 183 are formed on thefirst conductive type semiconductor layer 130 and the second conductivetype semi-conductor layer 170, respectively. As a result, a horizontaltype UV light emitting device as shown in FIG. 12 can be provided.

FIG. 13 to FIG. 16 are sectional views of a UV light emitting deviceaccording to a further exemplary embodiment and a method of fabricatingthe same. The UV light emitting device shown in FIG. 13 to FIG. 16 canbe fabricated from the UV light emitting device of FIG. 7. Hereinafter,a method of fabricating the UV light emitting device according to thisexemplary embodiment will be described.

Referring to FIG. 13, a support substrate 193 is formed on the secondconductive type semiconductor layer 170.

The support substrate 193 can be an insulation substrate, a conductivesubstrate, or a circuit board. For example, the support substrate 193can be a sapphire substrate, a gallium nitride substrate, a glasssubstrate, a silicon carbide substrate, a silicon substrate, a metalsubstrate, a ceramic substrate, and the like. In addition, the supportsubstrate 193 can be formed on the second conductive type semiconductorlayer 170 via bonding, whereby a bonding layer (not shown) can befurther formed between the support substrate 193 and the secondconductive type semiconductor layer 170 to bond the support substrate193 and the second conductive type semiconductor layer 170 to eachother.

The bonding layer can include a metallic material, for example, AuSn.The bonding layer including AuSn provides eutectic bonding between thesupport substrate 193 and the second conductive type semiconductor layer170. In the structure wherein the support substrate 193 is a conductivesubstrate, the bonding layer electrically connects the second conductivetype semiconductor layer 170 to the support substrate 193.

Furthermore, a reflective layer (not shown) can be further formedbetween the support substrate 193 and the second conductive typesemiconductor layer 170. The reflective layer can include a reflectivemetal layer (not shown) and a barrier metal layer (not shown), which canbe formed to cover the reflective metal layer.

The reflective metal layer can be formed by deposition. The reflectivemetal layer can serve to reflect light and can act as an electrodeelectrically connected to the second conductive type semiconductor layer170. Thus, it is desirable that the reflective metal layer include amaterial capable of forming ohmic contact while exhibiting highreflectivity with respect to UV light. The reflective metal layer caninclude at least one metal of, for example, Ni, Mg, Pt, Pd, Rh, W, Ti,Al, Ag, and Au. On the other hand, the barrier layer preventsinter-diffusion between the reflective metal layer and other materials.Accordingly, it is possible to prevent increase in contact resistanceand decrease in reflectivity due to damage to the reflective metallayer. The barrier layer can include Ni, Cr, Ti, W, Pt, and the like,and can be composed of multiple layers.

Alternatively, a transparent electrode can be further formed between thesupport substrate 193 and the second conductive type semiconductor layer170, and can include at least one of conductive oxides such as ITO, IZOand AZO, and a metallic material such as Ni/Au.

Referring to FIG. 14, the growth substrate 110 is separated from thefirst conductive type semiconductor layer 130. Particularly, the growthsubstrate 110 can be separated from the base nitride layer 123 or thebuffer layer 121.

Separation of the growth substrate 110 from the first conductive typesemiconductor layer 130 can be realized by laser lift-off. As shown inFIG. 14, the base nitride layer 123 can be decomposed by irradiating thebase nitride layer 123 with a laser beam (L) in a direction from thegrowth substrate 110 to the first conductive type semiconductor layer130, followed by separating the growth substrate 110 from the firstconductive type semiconductor layer 130. Here, the growth substrate 110can be a sapphire substrate and the base nitride layer 123 can includeGaN or AlGaN.

According to this exemplary embodiment, the base nitride layer 123including GaN or AlGaN can be interposed between the first conductivetype semiconductor layer 130 and the growth substrate 110, therebyallowing easy separation of the growth substrate 110 even using a KrFexcimer laser. Accordingly, it is possible to solve difficulty inseparation of the growth substrate through laser lift off in fabricationof a typical UV light emitting device.

Further, the UV light emitting device, which includes the buffer layer121 including GaN and the base nitride layer 123 including GaN or AlGaNhaving a relatively higher composition ratio of Ga, has a higherprobability of generating cracks in the first conductive typesemiconductor layer 130 than a UV light emitting device including an AlNbuffer layer. That is, in the structure wherein a nitride semiconductorlayer having a relatively higher composition ratio of Ga is formedbetween the sapphire substrate and the first conductive typesemiconductor layer 130, the probability that cracks occur due to stressapplied to the first conductive type semiconductor layer 130 is furtherincreased. Accordingly, conventionally, it is difficult to form thebuffer layer 121 including GaN and the base nitride layer 123 includingGaN or AlGaN having a relatively higher composition ratio of Ga betweenthe growth substrate 110 and the first conductive type semiconductorlayer 130 to prevent generation of cracks in the first conductive typesemiconductor layer 130.

However, according to the exemplary embodiment, since the anti-crackinglayer 140 is formed, it is possible to prevent generation of cracks inthe first conductive type semiconductor layer 130 even when the bufferlayer 121 including GaN and the base nitride layer 123 including GaN orAlGaN having a relatively higher composition ratio of Ga are formedbefore formation of the first conductive type semiconductor layer 130.Accordingly, a laser lift-off process can be applied to the process ofseparating the growth substrate 110 in fabrication of a vertical typelight emitting device or a flip-chip type light emitting device fromwhich the growth substrate 110 is separated. Accordingly, the exemplaryembodiments of the present disclosure provide a method of fabricating aUV light emitting device, which allows easy separation of the growthsubstrate 110, and a UV light emitting device fabricated by the same.

However, the present disclosure is not limited thereto, and additionallayers (for example, a sacrificial layer) can be further formed betweenthe growth substrate 110 and the semiconductor layers such that thegrowth substrate 110 can be separated by chemical lift-off, stresslift-off or thermal lift-off. Alternatively, the growth substrate 110can be removed by a physical/chemical process such as grinding andlapping.

Referring to FIG. 15, after separation of the growth substrate 110,other remaining semiconductor layers (for example, remaining materialson the base nitride layer 123 and/or the buffer layer 121) on the firstconductive type semiconductor layer 130 can be removed to expose onesurface of the first conductive type semiconductor layer 130. Theremaining layers placed on the first conductive type semiconductor layer130 can be removed by chemical and/or physical methods, or etching, forexample, at least one process selected from CMP, lapping, wet etching,and dry etching.

Referring to FIG. 16, a first electrode 191 is formed on the firstconductive type semiconductor layer 130, thereby providing a vertical UVlight emitting device, as shown in FIG. 16. In some exemplaryembodiments, before or after formation of the first electrode 191, aroughness 130R can be further formed on the first conductive typesemiconductor layer 130 by increasing surface roughness thereof.

Increasing the surface roughness of the first conductive typesemiconductor layer 130 can be performed using dry etching, wet etching,and electrochemical etching, for example, PEC (photo-enhanced chemical)etching, etching using a sulfuric-phosphoric acid solution, or etchingusing a hydroxide solution (for example, KOH, NaOH). The roughnessvaries depending upon etching conditions, and can have an average heightof, for example, 1.5 μm or less. The roughness can improve lightextraction efficiency of the UV light emitting device according to theexemplary embodiments.

In other exemplary embodiments, increasing the surface roughness of thefirst conductive type semiconductor layer 130 can be performed before orafter formation of the first electrode 191. In addition, the roughness130R cannot be formed in a region of the first electrode 191 on thesurface of the first conductive type semiconductor layer 130. However,the present disclosure is not limited thereto, and the roughness 130Rcan be selectively formed in the region of the first electrode 191 bytaking into account contact resistance between the first electrode 191and the first conductive type semi-conductor layer 130.

The first electrode 191 can be formed on the first conductive typesemiconductor layer 130 by deposition and lift-off, and can be composedof a single layer or multiple layers. The first electrode 191 caninclude a metal such as Ti, Pt, Au, Cr, Ni, and Al, and can form ohmiccontact with the first conductive type semiconductor layer 130.

Although the vertical type light emitting device having the growthsubstrate 110 removed therefrom has been described in the aboveexemplary embodiments described with reference to the accompanyingdrawings, it should be understood that the present disclosure is notlimited thereto. The fabrication method according to the exemplaryembodiments can also be applied to a flip-chip type light emittingdevice from which the growth substrate 110 is removed.

Although some exemplary embodiments have been described herein, itshould be understood that these embodiments are given by way ofillustration only, and that various modifications, variations andalterations can be made by those skilled in the art without departingfrom the spirit and scope of the invention.

1. A UV light emitting device comprising: a first conductive typesemiconductor layer; an anti-cracking layer disposed on the firstconductive type semiconductor layer; an active layer disposed on theanti-cracking layer; and a second conductive type semiconductor layerdisposed on the active layer, wherein the anti-cracking layer includesfirst lattice points and second lattice points that are disposed at aninterface between the first conductive type semiconductor layer and theanti-cracking layer, and the first lattice points are connected tolattices of the first conductive type semiconductor layer, and thesecond lattice points are not connected to the lattices of the firstconductive type semiconductor layer.
 2. The UV light emitting device ofclaim 1, wherein, at the interface between the first conductive typesemiconductor layer and the anti-cracking layer, the anti-cracking layerhas a higher density of lattice points per unit area than the firstconductive type semiconductor layer.
 3. The UV light emitting device ofclaim 1, wherein the first conductive type semiconductor layer includesa crack induction portion in which a lattice distance graduallyincreases in an upward direction.
 4. The UV light emitting device ofclaim 3, wherein a horizontal lattice distance in an uppermost portionof the crack induction portion is greater than an average horizontallattice distance in the first conductive type semiconductor layer. 5.The UV light emitting device of claim 3, wherein at least some of thesecond lattice points are positioned on the crack induction portion. 6.The UV light emitting device of claim 1, wherein the anti-cracking layerincludes a first layer and a second layer formed under the first layer,wherein the first layer includes a lattice point not connected to anylattices of the second layer at an interface between the first layer andthe second layer.
 7. The UV light emitting device of claim 6, whereinthe anti-cracking layer has a super lattice structure.
 8. The UV lightemitting device of claim 1, wherein each of the first conductive typesemiconductor layer and the anti-cracking layer includes a nitride-basedsemiconductor including one of Al and Ga.
 9. The UV light emittingdevice of claim 8, wherein the anti-cracking layer further includesindium (In), the active layer has a multi-quantum well structureincluding barrier layers and well layers, and the barrier layer includesa nitride-based semiconductor including Al, Ga and In.
 10. The UV lightemitting device of claim 1, further including: a growth substratedisposed under the first conductive type semiconductor layer, whereinthe growth substrate has a higher coefficient of thermal expansion thanthe first conductive type semiconductor layer.
 11. The UV light emittingdevice of claim 1, further including: a super lattice layer interposedbetween the anti-cracking layer and the active layer.
 12. The UV lightemitting device of claim 1, further including: a first electrodedisposed under the first conductive type semiconductor layer andelectrically connected to the first conductive type semiconductor layer;and a second electrode disposed on an upper side of the secondconductive type semiconductor layer and electrically connected to thesecond conductive type semiconductor layer.
 13. The UV light emittingdevice of claim 1, wherein the anti-cracking layer has a thickness of 5nm to 15 nm.
 14. A UV light emitting device comprising: a firstconductive type semiconductor layer; an anti-cracking layer disposed onthe first conductive type semiconductor layer; an active layer disposedon the anti-cracking layer; and a second conductive type semiconductorlayer disposed on the active layer, wherein a portion above an interfacebetween the first conductive type semiconductor layer and theanti-cracking layer has a higher lattice density than a portion underthe interface.
 15. The UV light emitting device of claim 14, wherein theanti-cracking layer includes a lattice not connected to a lattice of thefirst conductive type semiconductor layer.
 16. A method of fabricating aUV light emitting device, comprising: forming a first conductive typesemiconductor layer on a growth substrate; forming an anti-crackinglayer on the first conductive type semiconductor layer; forming anactive layer on the anti-cracking layer; and forming a second conductivetype semiconductor layer on the active layer, wherein the anti-crackinglayer is formed at a lower growth temperature than the first conductivetype semiconductor layer, and the forming the anti-cracking layerincludes forming first lattice points not connected to lattices of thefirst conductive type semiconductor layer.
 17. The method of fabricatinga UV light emitting device of claim 16, wherein, during the formation ofthe anti-cracking layer, an inner temperature of a growth chamber isgradually decreased for at least some period of time.
 18. The method offabricating a UV light emitting device of claim 17, wherein the firstconductive type semiconductor layer is grown at a first temperature, theactive layer is grown at a second temperature lower than the firsttemperature, and the anti-cracking layer is grown during lowering thetemperature from the first temperature to the second temperature. 19.The method of fabricating a UV light emitting device of claim 18,further including, during lowering the temperature from the firsttemperature to the second temperature, forming a crack induction portionin the first conductive type semiconductor layer, and forming firstlattice points on the crack induction portion, the first lattice pointsnot connected to lattices of the first conductive type semiconductorlayer of the anti-cracking layer.
 20. The method of fabricating a UVlight emitting device of claim 16, wherein the forming the anti-crackinglayer further includes forming second lattice points connected tolattices of the first conductive type semiconductor layer.
 21. Themethod of fabricating a UV light emitting device of claim 16, whereinthe forming the anti-cracking layer includes growing the anti-crackinglayer using remaining sources among sources introduced into a growthchamber to form the first conductive type semiconductor layer instead ofintroducing a separate source into the growth chamber during formationof the anti-cracking layer.